1. Field of the Invention
The present invention relates to a solid state image sensor.
2. Description of the Prior Art
In a conventional solid state image sensor such as an image sensor for a conventional interline transfer system, an electrode row of CCDs (charge coupled devices), a row of MOS capacitors and an OFD (overflow drain) are arranged alternately in the order named. One electrode, one MOS capacitor, and one OFD constitute one picture element. When such an image sensor is operated, the charged stored on the MOS capacitor is transferred to the CCD and is read out through the electrode. When the charge stored on the MOS capacitor is excessive, the extra charge is removed by the OFD. A correct image of one picture element is picked up by the functions of the electrode of the CCD, the MOS transistor and the OFD. It is known that in an image pickup device, better resolution is obtained with a greater number of picture elements. Due to this, various studies are being made for attaining an image sensor with a greater number of picture elements. However, with the conventional image sensor as described above, the electrode of the CCD, the MOS capacitor and the OFD are arranged horizontally to constitute one picture element so that it is difficult to change the pitch of the picture elements in the horizontal direction to accommodate a great number of picture elements.